mercoledì 25 ottobre 2006
Spinal cord injury without radiographic abnormality (SCIWORA)
History: A 2-year-old girl presents to the emergency department status post motor vehicle collision. She was restrained appropriately in a car seat and has no obvious injury on initial exam. CTs of the head, cervical spine, chest, abdomen, and pelvis were performed. The initial CT exams demonstrated a minimally displaced iliac wing fracture, but were otherwise normal. A detailed neurological examination of the patient revealed bilateral lower extremity paralysis and sensory deficit. The head and neck CT scan was negative.
Figure 1: The sagittal T2 weighted image shows an interruption in the cord below the cervicothoracic junction with edema extending above and below the level of transection.
Diagnosis: Spinal cord injury without radiographic abnormality (SCIWORA)
SCIWORA was initially described as a distinct disease in 1982, when MRI was not routinely utilized in evaluation of spinal cord injury (SCI). Pang and Pollack’s criteria for SCIWORA are: objective, posttraumatic myelopathy without vertebral subluxation or fracture as seen on plain x-ray films. Typically, there is no identifiable c-spine injury on CT imaging as well. In patients older than 16, SCI is usually associated with vertebral fracture. From infancy to age 16, SCI injury is rare, but frequently occurs without vertebral trauma. Outcomes are typically poorer with children under 8.
The phenomenon is thought to be related to weaker paraspinal muscle control, larger relative head size, and a more horizontal positioning of the facets in children. Also, in the thoracolumbar spine, there is a mismatch in the elasticity of the tissue comprising the spinal column vs the elasticity of the cord itself; the former can endure much greater distraction than the latter.
Currently with MRI, we are able to image the cord pathology in SCIWORA. Several different injury patterns are recognized on MR imaging: transection, contusive hemorrhage, traumatic edema, and concussion. Transection is seen as a complete disruption in the cord. Contusive hemorrhage and traumatic edema appear as focal, intramedullary signal abnormalities. Concussion is diagnosed when the cord appears normal or if there is equivocal, intramedullary, heterogeneous T2 signal corresponding to the level of clinical deficit. The severity of injury depicted on MRI correlates with long-term neurologic dysfunction with transection corresponding to complete and permanent deficit, and concussion corresponding to complete neurologic recovery.